Aftereffects: How Japan Can Improve Its Earthquake, Tsunami Defenses

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Japan's buildings may have mostly survived the massive 8.9
magnitude earthquake that struck last Friday, but thousands of
people died because of the deadly tsunami that followed and swept
away entire coastal towns. Now the Japanese have the chance to
rebuild even stronger defenses to safeguard the lives of its
citizens, experts say.

The country has one of the most sophisticated
earthquake and tsunami warning systems in the world, as well
as seawalls, fortlike floodgates and some tsunami shelters. Yet
the devastating loss of life suggests that not enough tsunami
shelters existed to give people safe haven above the waves – and
those that exist don't follow any one standard.

"There are so many kinds of tsunami shelters in Japan," said
Harry Yeh, a civil engineer at Oregon State University in
Corvallis. "There is no standard design at all for evacuation
buildings. That's the reason we cannot follow [for U.S. building
shelters]."

More disaster was prevented because of Japan's stringent building
code that requires new buildings to hold up against collapse
during
maximum-event earthquakes. The country also has thousands of
seismic-protective systems to protect important buildings such as
hospitals, along with some apartment and office buildings.

But many of the systems undergo less rigorous hazard analysis and
testing compared to the systems in quake-prone California,
according to Michael Constantinou, a civil engineer at the
University of Buffalo in Buffalo, N.Y. Japanese systems are also
designed for lower level earthquakes than their California
counterparts, in part because of the choice of technology.

"Bridges in Japan are designed for higher earthquake hazards than
the buildings next to them," Constantinou told
InnovationNewsDaily. "This, in my opinion, is problematic."

The main loss of life in Japan came from the tsunami spawned
by the earthquake. Such tragedy occurred despite Japan having
the best tsunami defenses in the world and a "very impressive"
warning system, said Yeh at Oregon State University.

Yeh was watching a Japanese TV channel when he saw a tsunami
warning pop up just five minutes after the earthquake. The first
waves arrived 30 minutes after the earthquake, which left many
coastal villagers without time to reach safety – if any higher
ground or shelters existed nearby. Cities such as Tokyo fared
better with their more extensive seawalls and floodgates.

Some Japanese tsunami shelters resemble towers, while others
merely involve a platform sitting atop concrete pillars. But even
that patchwork collection of shelters beats the total lack of
tsunami shelters in the U.S.

Tsunami experts had previously scoffed at the idea of even
building tsunami shelters – at least until the 2004 Indian Ocean
Tsunami killed 230,000 people. That led to the realization that
even educating people about fleeing the coast might not save
their lives.

"Even if we educate people to go to higher ground, there may be
no higher ground," Yeh said in a phone interview with
InnovationNewsDaily.

The first proposed U.S. tsunami shelter is designated to double
as the town hall for Cannon Beach, Ore., but only if the town can
find the funding. Yeh and his colleagues have been working on
simulation models of the tsunami
forces and evacuation procedures for such a shelter.

Steady on the shaking

Japan's bitter experience with tsunamis has naturally gone
hand-in-hand with its history of earthquakes. The country went on
a frenzy of quakeproofing following the 1995 Kobe earthquake that
killed more than 6,400 people, and now has the largest array of
such protective systems in the world.

"It's not something you can do overnight, but over last 15 years
practically every important building in Japan has been fitted
with these systems," Constantinou said. "Even in some apartment
buildings, they proceeded with application of this technology."

The thousands of protective systems include so-called seismic
isolators that protect a building similar to how shock absorbers
cushion passengers in a car. In Japan, many buildings sit atop
bearings which consist of stacked and bonded layers of rubber and
steel. The rubber allows for horizontal stretching during a
quake.

Still, such rubber-based systems can only stretch so far during
the
most massive earthquakes. California has favored so-called
friction pendulum isolators that use a lubricated slider trapped
between steel plates to permit even greater stresses from quakes,
but Japan has been slow to install such systems, Constantinou
said.

Both Japan and California also use steel braces attached
throughout a structure to dissipate some of the earthquake
energy, as well as more advanced "viscous dampers" that resemble
steel pistons.

California requires intensive surveys to figure out the
site-specific seismic hazard for each building, whereas Japan
uses a standard suite of recorded earthquake motions as a general
rule for installing such systems – something that is
"unacceptable" in California.

"Applications in Japan consider a lower level earthquake for the
design, [because] the displacement capacity of the isolation
systems is much less," Constantinou explained. "Also, review and
plan-checking appear not as rigorous as in California."

Constantinou seemed certain that Japan would apply even more
rigorous standards in the wake of its latest disaster. He also
acknowledged the huge challenge Japan faced in the "one-two
combination" of the earthquake and tsunami.

"This is really a catastrophe," Constantinou said. "But I think
they did really well."